Seal for use with medical device and system

ABSTRACT

A seal adapted for use with medical devices is provided with a lead having a distal tip electrode. The distal tip of the lead is adapted for implantation on or about the heart and for connection to a system for monitoring or stimulating cardiac activity. The lead can include a fixation helix for securing the electrode to cardiac tissue. The lead assembly can alternatively include an open lumen lead tip. A seal is provided within the lead tip assembly such that the seal is expanded to prevent or limit further entry of fluids through the lead tip. The seal includes an expandable matrix, such as a hydrogel. The seal is formed on or within the lead when the lead and the seal comes into contact with a fluid and expands. The seal is also formed as a plug which is deployed through the medical device, and expands as the plug absorbs fluid. A housing incorporating the seal can also be attached to a portion of the medical device to provide the seal.

This application is a continuation of U.S. application Ser. No.09/970,195, filed Oct. 2, 2001, now U.S. Pat. No. 6,901,288, which is acontinuation of application Ser. No. 09/579,765, filed on May 26, 2000,now abandoned, which is a divisional of U.S. application Ser. No.09/133,310, filed on Aug. 12, 1998, now U.S. Pat. No. 6,240,321, thespecifications of all of which are herein incorporated by reference

FIELD OF THE INVENTION

The present invention relates generally to medical devices, such asleads and catheters. More particularly, it pertains to expandable sealsfor medical devices such as leads and catheters.

BACKGROUND OF THE INVENTION

Leads implanted in or about the heart have been used to reverse (i.e.,defibrillate or cardiovert) certain life threatening arrhythmias, or tostimulate contraction (pacing) of the heart. Electrical energy isapplied to the heart via the leads to return the heart to normal rhythm.Leads have also been used to sense in the atrium or ventricle of theheart and to deliver pacing pulses to the atrium or ventricle. The samelead used to sense the condition is sometimes also used in the processof delivering a corrective pulse or signal from the pulse generator ofthe pacemaker.

Cardiac pacing may be performed by the transvenous method or by leadsimplanted directly onto the ventricular epicardium. Most commonly,permanent transvenous pacing is performed using a lead positioned withinone or more chambers of the heart. A lead, sometimes referred to as acatheter, may be positioned in the right ventricle or in the rightatrium through a subclavian vein, and the lead terminal pins areattached to a pacemaker which is implanted subcutaneously. The lead mayalso be positioned in both chambers, depending on the lead, as when alead passes through the atrium to the ventricle. Sense electrodes may bepositioned within the atrium or the ventricle of the heart.

Pacemaker leads represent the electrical link between the pulsegenerator and the heart tissue which is to be excited. These pacemakerleads include single or multiconductor coils of insulated wire having aninsulating sheath. The coils provide a cylindrical envelope, many timesreferred to as a lumen, which provides a space into which a stiffeningstylet can be inserted. The conductive coil is connected to an electrodein an electrode assembly at a distal end of a pacing lead.

After the electrode assembly is positioned at a desired location withinthe heart, it is desirable to provide some method for securing theelectrode assembly at that location. One approach is to use a passivedevice which has structure to allow for tissue growth surrounding thestructure to affix the electrode assembly to the heart. Another approachis to use an active device where mechanical fixation devices are used tofirmly anchor the electrodes in the heart. One type of mechanicalfixation device used is a corkscrew, or a helix. During placement of thelead, the tip of the lead travels intravenously through veins and theheart. While traveling through the veins, the helix at the tip of thelead may snag or attach to the side wall of the vein. Since this ishighly undesirable as it may cause damage or other complications to apatient, retractable helixes have been provided for leads.

The practitioner must maintain the electrode pressed against the wall ofthe cavity before shifting the screw. When the screw is shifted, theelectrode may be correctly in contact with the wall, and the fixationscrew, as it travels out of the body of the electrode, penetrates andbecomes hooked in the tissue of the wall. Alternatively, the electrodemay stop short of the wall of the cavity and it may be necessary for thepractitioner to start again by retracting the screw and then turning thehelix out again into the cardiac tissue. Thus, it is important for thehelix to rotate freely within the electrode.

During use, the lead provides and receives critical information to andfrom the heart. The lead, therefore, must remain in sufficient operativecondition without interference from entry of bodily fluids. To prevententry of bodily fluids into the lead, a seal can be provided at thedistal end of the lead. Conventional leads often use O-rings or punctureseals to seal the distal end of the lead from entry of bodily fluids.The O-ring seals can be difficult to manufacture due to dimensionalconstraints which also affects the extension/retraction mechanism of thelead, as well as the effectiveness of the seal. Puncture seals also mayincrease the difficultly of using the helix, since the helix needs topuncture the seal and the puncture seals can increase the frictionbetween the extension mechanism and the seal. The friction makes it moredifficult to extend or retract the extension mechanism and the helix. Inaddition, the structural integrity of the puncture seal can bejeopardized if the seal continues to tear from repeated movement and/orstress from the fixation screw.

Accordingly, there is a need for a lead which is sufficiently sealedfrom the environment. What is further needed is a seal which does notinterfere with the extension and retraction of the helix.

SUMMARY OF THE INVENTION

A body-implantable lead assembly is provided comprising a lead, one endbeing adapted to be connected to an electrical supply for providing orreceiving electrical pulses. The lead further comprises a distal tipwhich is adapted to be connected to tissue of a living body. The leadalso has a sheath of material inert to body materials and fluids and atleast one conductor extending through the lead body.

The distal tip electrode is adapted for implantation proximate to orwithin the heart while connected with a system for monitoring orstimulating cardiac activity. In another embodiment, the distal tipelectrode assembly is adapted for implantation proximate to the heartwhile connected with a system for monitoring or stimulating cardiacactivity. The distal tip electrode includes, in one embodiment, anelectrode tip, a mesh screen disposed at a distal end of the electrodetip, a fixation helix disposed within the electrode tip, and a hydrogelseal. The helix is retractable, and is in contact with a movementmechanism. The movement mechanism provides for retracting the helix,such as during travel of the electrode tip through veins. In anotherembodiment, the electrode tip further includes a piston for moving thehelix. The piston can further include a slot for receiving a stylet.When engaged and rotated, the piston provides movement to the helix. Thepiston is coated with the hydrogel seal, in one embodiment, which isadapted to expand upon contact with bodily fluid.

In another configuration, a distal tip electrode is provided which isadapted for implantation proximate to the heart, while optionallyconnected with a system for monitoring or stimulating cardiac activity.The distal tip electrode includes a seal comprised of an expandablematrix which is adapted to expand upon contact with fluid. The seal canbe in the form of a plug which is inserted into the electrode, or amedical device, using an advancing tool. The plug can be molded of theexpandable material into a variety of shapes, for instance a ring, orincluding a tapered surface. The ring shape can also be used forsurrounding an internal lead structure disposed within the lead. Theplug can optionally include features which frictionally engage anencompassing surface and prevent premature removal of the advancingtool. In another embodiment, the seal is in the form of an end cap whichis affixed to the distal tip of the electrode. Alternatively, theexpandable matrix is disposed on the interior of a housing which issecured to the electrode.

The provided medical device, which includes an electrode tip, suppliesan extension/retraction mechanism which is sealed from exposure tofluids. The lead avoids deterioration of its function by entry of liquidinside the lead, owing to the provision of a highly effective seal whichdoes not interfere with the helix. In addition, the seal remainsfunctional when the lead is removed for short periods of time from anenvironment filled or partially filled with fluid. Yet another advantageis that the lead and the seal permit rotating the extension/retractionmechanism until it penetrates the cardiac tissue without limitation onthe number of rotations until proper anchorage has been achieved, andwithout significant friction imparted to the extension/retractionmechanism.

These and other embodiments, aspects, advantages, and features of thepresent invention will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the art byreference to the following description of the invention and referenceddrawings or by practice of the invention. The aspects, advantages, andfeatures of the invention are realized attained by means of theinstrumentalities, procedures, and combinations particularly pointed outin the appended claims and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view illustrating a lead constructed inaccordance with one embodiment of the present invention.

FIG. 2 is a cross-sectional view of an electrode tip of a lead formonitoring and stimulating the heart constructed in accordance with oneembodiment of the present invention.

FIG. 3A is a cross-sectional view of an electrode tip of a lead formonitoring and stimulating the heart constructed in accordance with oneembodiment of the present invention.

FIG. 3B is a cross-sectional view of an electrode tip of a lead formonitoring and stimulating the heart constructed in accordance with oneembodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a system for deliveringsignals to the heart constructed in accordance with one embodiment ofthe present invention.

FIG. 5 is a table illustrating the expansion for the expandable matrixconstructed in accordance with one embodiment of the present invention.

FIG. 6 is a table illustrating the amount of expansion for theexpandable matrix constructed in accordance with another embodiment ofthe present invention.

FIG. 7 is a perspective view of a plug for sealing a medical deviceconstructed in accordance with one embodiment of the present invention.

FIG. 8 is a cross-sectional view of a lead for monitoring andstimulating the heart constructed in accordance with one embodiment ofthe present invention.

FIG. 9 is a cross-sectional view of a lead for monitoring andstimulating the heart constructed in accordance with one embodiment ofthe present invention.

FIG. 10 is a cross-sectional view of a lead for monitoring andstimulating the heart constructed in accordance with one embodiment ofthe present invention.

FIG. 11 is a cross-sectional view of a lead for monitoring andstimulating the heart constructed in accordance with one embodiment ofthe present invention.

FIG. 12 is a cross-sectional view of a lead for monitoring andstimulating the heart constructed in accordance with one embodiment ofthe present invention.

FIG. 13 is a cross-sectional view of a lead for monitoring andstimulating the heart constructed in accordance with one embodiment ofthe present invention.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that structuralchanges may be made without departing from the spirit and scope of thepresent invention. Therefore, the following detailed description is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims and their equivalents.

One embodiment of a lead 10 is illustrated in FIG. 1. The lead 10, inone embodiment, comprises a lead body 11, and extends from a proximalend 32 to a distal end 30. An elongate conductor is contained within thelead body 11, and a lead tip 20 is disposed proximate the distal end 30.In one embodiment, an electrode tip assembly 24 is contained in the leadtip 20 (FIG. 2). In another embodiment, the lead tip 20 comprises anopen lumen lead tip (FIGS. 3A and 3B). In addition, a stylet 14 isshown, which in one embodiment is inserted into the lead body 11.

A helix 100 (FIG. 2) comprises an electrical conductor coil, iscontained in the retractable lead tip assembly 24, in anotherembodiment. The helix 100 extends and retracts by rotation of the stylet14, as will be discussed further below. Although a brady lead body isshown, other medical devices or other leads, such as tachy leads couldalso be used. In one embodiment, the lead body 11 is at least partiallycovered by a biocompatible insulating material 22. Silicone rubber orother insulating material can be used for covering the lead body 11.

In one embodiment, the helix 100 is formed of electrically conductivematerial offering low electrical resistance and which is also resistantto corrosion by body fluids. In another embodiment, the helix 100 may becoated with an insulative material. A platinum-iridium alloy is anexample of a suitable conductive material. Another example is aconductive helix partially coated with Parylene. The Parylene insulativecoating effectively increases in vitro “pacing impedance”. Applicationof Parylene to the metallic fixation helix produces the desired increasein impedance compared to an uninsulated helix as well as other existingdesigns. Alternatively, in another configuration, the helix 100 iselectrically inactive. The helix 100 can be made electrically active orinactive to change sensing and pacing characteristics as needed.

Referring to FIG. 2, the helix 100 of the lead 10, in one embodiment,defines a lumen 102 therethrough and thereby is adapted to receive astiffening stylet 14 that extends through the length of the lead 10. Thelumen 102, however, can also be defined by other portions of theelectrode tip assembly 24. The stylet 14 (FIG. 1) stiffens the lead 10,and can be manipulated to introduce an appropriate curvature to the lead10, facilitating the insertion of the lead 10 into and through a veinand through an intracardiac valve to advance the distal end 30 of thelead 10 into the heart, for example into the right ventricle of theheart. A stylet knob 12 (FIG. 1) is coupled with the stylet 14 forrotating the stylet 14 and advancing the helix 100 into tissue of theheart.

In another embodiment, the lead 10 has an electrode tip 120 which isprovided with a mesh screen 130. The mesh screen 130 covers at least aportion of an end surface 112 of the lead 10, and serves as thepacing/sensing interface with cardiac tissue. If the helix 100 iselectrically active, it too can help serve as a pacing or sensinginterface. The mesh screen 130 is of a porous construction, made ofelectrically conductive, corrosion resistant material. Using a meshscreen 130, for example having a porous construction, advantageouslyallows for fibrotic ingrowth. This provides for a further anchoring ofthe electrode tip 120 and also increases the sensing capability of thelead 110 by increasing the surface area in contact with the cardiactissue. The impedance of the mesh screen can be also controlled byproviding a partially insulating mesh screen. The mesh screen 130, inone embodiment, is attached to an electrode collar 132, which can beelectrically active.

Disposed within the lead 10, in one embodiment, is a lead fastener forsecuring the lead 10 to cardiac tissue. The lead fastener can bedisposed along the radial axis 15 (FIG. 2) of the electrode lead 10. Inone embodiment, the lead fastener comprises a fixation helix 100. Thefixation helix 100 can be made electrically active or inactive asdiscussed above. Using a conductor coil such as helix 100 has been shownto be capable of withstanding constant, rapidly repeated flexing over aperiod of time which can be measured in years. The helix 100 is woundrelatively tightly, with a slight space between adjacent turns. Thisclosely coiled construction provides a maximum number of conductor turnsper unit length, thereby providing optimum strain distribution. Thespirally coiled spring construction of helix 100 also permits asubstantial degree of elongation, within the elastic limits of thematerial, as well as distribution along the conductor of flexingstresses which otherwise might be concentrated at a particular point.

Attached to the fixation helix 100, in one embodiment, is a piston 150.The piston 150 has a stylet slot 154 which is configured to mate withthe bladed locking stylet 14 at the stylet slot 154. The stylet slot 154acts as an interface between the stylet 14 and the helix 100. The stylet14, coupled the piston 150 at the stylet slot 154, extends and retractsthe fixation helix 100 when the stylet 14 is rotated. The piston 150 caneither be electrically active or inactive. The piston 150, in anotherembodiment, also has a base slot 152, which allows the piston 150 tomate with a base 160. The helix 100 with or without the piston form amovement mechanism which facilitates the implantation of the lead 10into a heart.

Fitted with a knob 162, as shown in FIG. 2, the base 160, in oneembodiment, mates with the base slot 152 of the piston 150. The base 160serves as a stop once the fixation helix 100 is fully retracted. Thebase 160, which can be electrically conductive, is adapted to allowpassage of a bladed locking stylet 14 and attachment of electrode coils.

A housing 140, which is electrically conductive in one embodiment,encapsulates the piston 150 and the fixation helix 100. In oneembodiment, the housing 140 is disposed about the piston 150, creatingan annular gap 156 therebetween. Insulation (not shown) is disposedabout the housing 140 and collar 132. A suitable material for theinsulation is, for example, silicone rubber, or other materials whichare inert and well tolerated by body tissue are also appropriate. Thehousing 140 is coupled with the electrode collar 132 and transmitselectrical signals from the electrode collar 132 to the base 160.

In another embodiment, the electrode tip 120 has a hydrogel seal 164disposed therein. In one embodiment, the piston 150 is coated with thehydrogel seal 164. In another embodiment, a portion of the helix 100 iscoated with the hydrogel seal 164. For example, a tight-wound portion151 of the helix 100 is coated with the hydrogel seal 164. The hydrogelseal 164 is adapted to expand upon contact with fluid and fill and sealoff the annular gap 156 between the piston 150 and the housing 140. Inone embodiment, the seal 164 prevents any blood flow through theelectrode tip 120. Alternatively, in another embodiment, the seal 164 isadapted to limit the bodily fluid which passes past the seal 164. Thehydrogel seal 164 is comprised of material which expands upon contact offluid. One suitable type of material is a hydrophilic polymer, forexample poly (2-hydroxyethyl methacrylate), polyvinyl alcohol, orpolyethylene oxide. Other examples include Thermedics TECOGEL,Thermedics TECOPHILLIC, and polyvinyl pyrrolidone. Alternatively, othermaterials which are expandable upon contact with fluid could also beused. Once expanded to fill the annular gap 156, the hydrogel seal 164is lubricious, thereby allowing rotation of the piston 150 and the helix100 via the stylet 14.

The hydrogel seal 164 is not limited to a retractable lead, and can beused on other medical devices such as catheters. FIGS. 3A and 3Billustrate another embodiment which includes an open lumen lead 180. Theopen lumen lead 180 has a lead body 182 extending to a lead tip 183,defining a lumen 184 therein. The lumen 184 is defined by an innersurface 188 of the lead body 182. The lumen 184 is used to manipulatethe lead 180 over a guidewire (not shown). Since no seal is typicallyprovided, blood and other bodily fluids can enter the lumen 184, leadingto complications. A hydrogel seal 186, in one embodiment, is disposed onthe inner surface 188 of the lead body 182, as shown in FIG. 3A. Thehydrogel seal 186 is adapted to expand upon contact with fluid and filland seal off the lumen 184. In one embodiment, the seal 186 prevents anyfurther flow of blood or bodily fluid through the lead tip 183.Alternatively, in another embodiment, the seal 186 is adapted to limitthe bodily fluid which passes past the seal 186. The hydrogel seal 186is comprised of material which expands upon contact of fluid. Uponcontact with fluid, the hydrogel seal 186 expands to fill the lumen 184as shown in FIG. 3B.

FIG. 4 illustrates another embodiment, showing a view of a lead 200adapted for delivering electrical pulses to stimulate the heart. Thelead 200 is not limited to any particular type of lead. The lead 200extends from a proximal end 202, which is adapted to connect withequipment which supplies electrical pulses, to a distal end 204 which isadapted to be inserted into the heart. Proximate to the distal end 204is an electrode tip 230. The electrode tip 230 includes a hydrogel sealor expandable matrix material (discussed below) disposed therein. Uponcontact with fluid, as discussed above, the hydrogel seal or theexpandable matrix material absorbs the fluid and expands to prevent orlimit additional fluid from entering through the electrode tip 230.

A connector terminal 210 is disposed near the proximal end 202 of thelead 200. The connector terminal 210 electrically connects the variouselectrodes and conductors within the lead 200 to a pulse generator andsignal sensor 240. The pulse sensor and generator 240 containselectronics to sense various electrical signals of the heart and alsoproduce current pulses for delivery to the heart, depending on the typeof lead 200 used. The pulse sensor and generator 240 also containselectronics and software necessary to detect certain types ofarrhythmias and to correct for them. The lead terminal connector 210provides for the electrical connection between the lead 200 and thepulse generator 240.

In another configuration, an expandable matrix can be used to seal amedical device, such as a lead tip assembly. The expandable matrix canbe molded and/or machined into a plug used as an external or internalseal, as will be further discussed below. Alternatively, the expandablematrix can be used as a coating on or in a base structure, whichstructure can be substantially rigid. The expandable matrix isbiocompatible. The expandable matrix is adapted to expand upon contactwith a fluid, and is effective in sealing fluids from further entry intothe medical device.

The composition of the expandable matrix, in one embodiment, generallyconsists of at least one water permeable polymeric material incombination with one or more osmotically active agents. One example of awater permeable polymeric material includes silicone. Otherbiocompatible elastomeric polymers include polyvinyl alcohol orpoly(ethylene oxide), or polyurethane. The expandable matrix includes atleast one osmotically active agent such as, glycerol, sodium chloride,or calcium chloride. Other equivalent agents can also be useful forforming the expandable matrix such as mannitol, glucose, dextran,potassium chloride, sodium phosphate, or any other non-toxic watersoluble material that does not adversely affect curing of the waterpermeable polymer.

The expandable matrix is adapted to absorb water upon contact with afluid environment. As water is absorbed, the matrix begins to swell inphysical size and continues to swell until, in one embodiment, theosmotically active agent is consumed. Alternatively, in anotherembodiment, the expandable matrix swells until the internal pressure ofthe matrix is matched by a source of external pressure of, for example,the polymer or structure surrounding the polymer. The rate of expansionand/or the amount of expansion can be controlled by the selection of thepolymer, the additive, and the particle size of the additive.

Other materials can be incorporated with the expandable matrix to yieldadditional advantages or results. For example, in one embodiment, theexpandable matrix could incorporate a radiopaque material so that thematrix can be visualized using a fluoroscope. In another configuration,pharmacologic additives can be incorporated with the expandable matrixsuch as dexamethasone sodium phosphate, which would cause expansion ofthe matrix and provide local pharmacologic therapy, such asanti-inflammatory action, thus improving the biocompatibility of thedevice. Alternatively, additives which would promote local bloodcoagulation can also be incorporated, such as calcium salts, intrinsicor extrinsic clotting factors.

The amount of osmotically active agent contained within the waterpermeable polymeric material can be varied, depending on the desiredresults. For instance, the rate of expansion or the total amount ofexpansion can be controlled by varying the relative amounts ofmaterials, which can be determined by testing the materials. In oneembodiment, the weight content of the osmotically active agent of theexpandable matrix ranges from 2%-50%. In another embodiment, the weightcontent of the osmotically active agent of the expandable matrix rangesfrom 10%-40% by weight.

In one embodiment, the total amount of expansion was measured for aexpandable matrix comprising water permeable polymeric material ofsilicone (Dow Corning MDX-4-4210) with an osmotically active agent ofglycerol. The amount of glycerol, by weight percentage, was varied from10% to 40%. The results of this testing are summarized in FIGS. 5 and 6.FIG. 5 illustrates the change in diameter of two matrix compositionsover time of exposure, which shows that the fastest change in diameteroccurs in the early stages of exposure. FIG. 5 also illustrates that thefastest change in diameter, i.e., the fastest rate of expansion,occurred in the early stages of the 40% glycerol/silicone matrix.However, this amount would vary for other water permeable polymericmaterials and/or other osmotically active agents. These resultsdemonstrate that the rate of expansion could be increased usingincreasing concentrations of glycerol. FIG. 5 also illustrates that thedimensions of the matrix containing 40% of glycerol returns toapproximately the initial diameter with prolonged exposure to fluid. Incontrast, the test sample containing 20% of glycerol maintains a stable,expanded dimension over the same prolonged exposure time.

FIG. 6 further compares final dimensions of the matrix material afterprolonged exposure for compositions ranging from 10% to 40% of glycerol,measured by weight. Of the samples tested, a glycerol content of 40%yields the fastest expansion. However, a maximum stable, over time,expanded matrix size occurs with the matrix containing 20% of glycerol.Thus, the amount of glycerol content can be manipulated to modify theexpansion of the expandable matrix upon initial contact with fluid aswell as contact with fluid over extended periods of time.

FIG. 7 illustrates one embodiment incorporating the expandable matrix asdiscussed above. A plug 300 is provided which, in one embodiment, ismolded from an expandable matrix which is adapted to expand upon contactwith fluid. Alternatively, the plug 300 can be coated with theexpandable matrix. The plug 300 extends from a first end 312 to a secondend 314, and, in one embodiment, is generally cylindrically shaped. Thefirst end 312 and the second end 314 define an intermediate portion 316therebetween. In one embodiment, the first end 312 includes a taperedportion 318. The tapered portion 318 facilitates implantation of theplug 300 into a medical device, or movement of the plug through narrowpassages.

The plug 300 is defined in part by an outer surface 320 which includesan outer diameter 322. In one embodiment, proximate the second end 314,the plug has a recess 328 therein. The recess 328 defines an innerdiameter surface 324 and an advancing surface 326. The recess 328 isadapted, in one embodiment, to receive an advancing tool (FIG. 8)therein, as will be further described below. The inner diameter surface324, in another embodiment, is adapted to frictionally engage theadvancing tool therein. Alternatively, the recess 328 can be configuredsuch that sufficient expansion of the plug 300 must occur before theadvancing tool could be removed from the recess 328.

In one configuration, the outer diameter 322 of the plug 300 has atleast one rib 330 disposed thereon. The at least one rib 330 can beconfigured in many different shapes. The at least one rib 330 is adaptedto project from the outer surface 320 of the plug 300. As the plug 300expands upon contact with fluid, the at least one rib 330 interfereswith further advancement of the plug 300 through an enclosing surfaceand permits the plug 300 to expand to fill a lumen in which the plug 300is disposed. As the plug 300 further expands, the at least one rib 330is compressed by an external surface of a lumen (FIG. 8) in which theplug 300 is received. In one configuration, a plurality of ribs 332 areprovided, which, in one embodiment, extend longitudinally along the plug300. As the plurality of ribs 332 are compressed, the plug 300 isretained by the enclosing surface to allow for removal of the advancingtool 460 (FIG. 8) therefrom.

FIG. 8 illustrates another embodiment of the present invention. In thisconfiguration, a plug 400 is received within a medical device 440. Theplug 400 is molded from an expandable matrix which is adapted to expandupon contact with fluid, as discussed above. Alternatively, the plug 400is coated with the expandable matrix. In one embodiment, the medicaldevice 440 comprises a lead 442 which is adapted to be implanted in oraround the heart. The lead 442 comprises a number of configurations suchas, although not limited to, those described above and shown in FIGS.1-4. Disposed within the lead 442 is a coil 446, which is contained byan outer body 448, and the lead 442 has a lumen 444 therein. The plug400 is adapted to seal the lumen 444 of the lead 442 upon expansion ofthe plug 400, which prevents bodily fluids from entering through thelead 442 and interfering with the performance of the lead 442.

The plug 400 extends from a first end 412 to a second end 414, and has atapered portion, in one embodiment, proximate to the first end 412. Inanother configuration, the plug 400 has a recess 428 therein, which isdisposed proximate the second end 414. The recess 428 is adapted toreceive a distal tip 462 of an advancing tool 460 therein. Once accessthrough the lumen 444 is no longer needed, the plug 400 can bepositioned within the medical device 440. The advancing tool 460 is usedto move the plug 400 through the lumen 444 of the medical device 440 andposition the plug 400 in an appropriate sealing location. The plug 400and/or the recess 428 can be modified as in the previous embodimentshown in FIG. 7 to facilitate removal of the advancing tool 460. Afterthe plug 400 has been positioned within the medical device 440, theadvancing tool 460 can be removed. Upon contact with fluid, the plug 400will begin to expand and seal the lumen 444 of the medical device 440.

In another configuration, as shown in FIG. 9, a plug 500 is providedwhich is coupled with a medical device 540. The plug 500 is molded froman expandable matrix which is adapted to expand upon contact with fluid,as discussed above. Alternatively, the plug 500 is coated with theexpandable matrix. In one embodiment, the medical device 540 comprises alead 542 which is adapted to be implanted in or around the heart. Thelead 542 can comprise a number of configurations such as, although notlimited to, those described above and shown in FIGS. 1-4. Disposedwithin the lead 542 is a coil 546, which is contained by a body havingan outer diameter 548, and the lead 542 has a lumen 544 therein. Thelead 542 extends to a distal end 552 where it abuts the plug 500 at anattachment surface 520. The plug 500 is adapted to seal the lumen 544 ofthe lead 542 upon expansion of the plug 500, which prevents bodilyfluids from entering through the lead 542 and interfering with theperformance of the lead 542.

The plug 500 is molded from an expandable matrix which is adapted toexpand upon contact with fluid. Alternatively, the plug 500 is coatedwith the expandable matrix. The plug 500 extends from a first end 512 toa second end 514, and in one embodiment has an outer surface shaped as acone 510. The plug has a first inner diameter 522 proximate the firstend 512 and a second inner diameter 524 proximate the second end 514.The second inner diameter 524 is, in one embodiment, larger than thefist inner diameter 522, forming a shoulder 526 therebetween.

The coil 546 of the lead 542, in one embodiment, extends past the distalend 552 of the lead 542 and is received by the second inner diameter 524of the plug 500. The coil 546, in one embodiment, is affixed to thesecond inner diameter 524 such that the coil 546 rests against theshoulder 526 of the plug 500. In another configuration, the coil 546 isfrictionally engaged by the surface of the second inner diameter 524. Inyet another embodiment, the coil 546 can be attached to the lead 542 ina number of manners including medical adhesive.

As the plug 500 is exposed to fluids, the surface of the first innerdiameter 522 begins to grow smaller and smaller until a seal is created.Once the first inner diameter 522 has been eliminated by the expansionof the expandable matrix, the lumen 544 of the medical device 540 iseffectively sealed off from further entry of fluids.

Illustrated in FIG. 10 is another configuration, wherein a plug 600 isprovided which is coupled with a medical device 640. In one embodiment,the medical device 640 comprises a lead 642 which is adapted to beimplanted in or around the heart. The lead 642 can comprise a number ofconfigurations such as, although not limited to, those described aboveand shown in FIGS. 1-4. Disposed within the lead 642 is a coil 646,which is contained by a lead body having an outer diameter 648, and thelead 642 has a lumen 644 therein. The lead 642 extends to a distal end652 where it abuts the plug 600 at an attachment surface 620.

The plug 600 comprises a housing 610 having an outer diameter 616 and aninner diameter 618. The housing 610 is formed from a rigid material hasexpandable matrix material 612 disposed within the inner diameter 618,where the expandable matrix material 612 is adapted to expand uponcontact with fluid, as discussed above. The housing 610 can be attachedto the medical device 640 in a variety of manners. For instance, in oneconfiguration, the housing 610 is laser welded to the medical device640. Alternatively, other attachment methods can also be used, such asresistance welding or adhesive bonding. The plug 600 is adapted to sealthe lumen 644 of the lead 642 upon expansion of the plug 600, whichprevents bodily fluids from entering through the lead 642 andinterfering with the performance of the lead 642.

The coil 646 of the lead 642, in one embodiment, extends past the distalend 652 of the lead 642 and is received by the inner diameter 618 of theplug 600. The coil 646, in one embodiment, is affixed to the innerdiameter 618. The coil 646 can be affixed to the inner diameter 618using adhesive or mechanical attachment methods. In anotherconfiguration, the coil 646 is frictionally engaged by the surface ofthe inner diameter 618.

As the plug 600 is exposed to fluids, the expandable matrix material 612swells and the inner diameter 618 begins to grow smaller and smalleruntil a seal 613 is created. Once the inner diameter 618 has beeneliminated by the expansion of the expandable matrix, the lumen 644 ofthe medical device 640 is effectively sealed off from further entry offluids.

In another configuration, as illustrated in FIG. 11, a medical devicesuch as a lead 700 is provided which has a cup 720 affixed thereto. Thecup 720 comprises, in one embodiment, a thin-walled structure which isreceived by the lead 700 around an outer diameter 728 of the cup 720.The cup 720 can be made from biocompatible metal alloys and/or rigidpolymers. In one embodiment, the cup 720 is attached at a distal end 702of the lead 700, for example, by welding the cup 720 to the conductorcoil 712 of the lead 700. Alternatively, the cup 720 can be attached tothe lead 700 in other manners.

In another embodiment, the cup 720 includes a first inner diameter 722and a second inner diameter 724, forming a shoulder 726 therebetween.Molded expandable material 740 is provided which rests upon the shoulder726 until expansion takes place. The molded expandable material 740 isformed from expandable matrix material, as discussed above in previousembodiments. Once the lead 700 has been implanted, and fluids contactthe molded expandable material 740, the material 740 expands until itcontacts the surface of the first inner diameter 722. The moldedexpandable material 740 can be provided in a variety of shapes toaccommodate the interior surface of the cup 720. In one configuration,the expandable material 740 is provided in the shape of a ring. The ringshape allows for access to a lumen 710 of the lead 700 duringimplantation, yet provides an effective seal after contact with fluid.

FIG. 12 illustrates yet another configuration of a lead 800. The lead800 has a lead body 810 containing a conductor coil 812 therein. Theconductor coil 812 defines a lumen 814 within the lead 800. Disposedwithin the lumen 814 of the lead body 810 is a secondary, internal leadstructure 820 having, in one embodiment, a distal electrode 822 and aproximal electrode. An annular gap 816 exists between the internal leadstructure 820 and the conductor coil 812. A plug 840 (shown prior toexpansion) is disposed between the internal lead structure 820 and theconductor coil 812, where the plug 840 is adapted to fill the gap 816upon contact with fluid. In one configuration, the plug 840 is molded ofthe expandable matrix as discussed in the earlier embodiments. Uponcontact with fluid, the plug 840 expands to the plug 842 and preventsfurther fluids from entering through the lumen 814 of the lead 800. Theplug 840 can be provided as a resident structure of the lead 800.Alternatively, the plug 840 can be advanced through the lumen 814 usingan advancing tool (FIG. 8), such as a stylet (not shown) after theinternal lead structure 820 has been placed. The plug 840 advantageouslyseals the lumen 814, and also maintains the internal lead structurewithin the lumen 814. In addition, the plug 840 allows for easymaneuvering of the internal lead structure 820 during placement of theinternal lead structure 820.

In FIG. 13, another embodiment of a lead 900 is illustrated. The lead900 has a lead body 910 encompassing, at least in part, a conductor coil912. A portion of the conductor coil 912 is exposed thereby forming anexposed electrode 914. The conductor coil 912 defines a lumen 916therein. The lumen 916, in conjunction with a guidewire, for example,can be used to position the lead 900 within the heart. However, thelumen 916 allows for entry of bodily fluids into the lead 900, which maylead to complications.

A plug 920 is provided which seals off the lumen 916 after the lead 900is properly positioned within the heart. The plug 920 is formed from theexpandable matrix material as discussed in the earlier embodiments. Theplug 920, in another embodiment, could also include a steroid to reducetissue inflammation. Upon contact with bodily fluid, the plug 920expands and seals off the lumen 916. The plug 920 is sized and adaptedto expand until it occupies enough of the lumen 916 to seal off harmfulentry of fluids. The components of the expandable matrix materialforming the plug 920 can be modified to provide the appropriate sizeplug as needed. The expanded plug 920 also provides physical support tothe exposed electrode 914 so that it is not inadvertently crushed.

To seal the lumen 916, the plug 920 must be properly positioned withinthe lead 900. An advancing tool 922 is used, in one embodiment, toproperly position the plug 920 within the lead 900. Alternatively, theplug 920 can be adapted to occupy the lead 900 as a resident structure,as discussed in the earlier embodiments. In one configuration, theadvancing tool 922 has a predetermined length which allows for the tool922 to be inserted into the lead 900 at a maximum of this predeterminedlength, which properly positions the plug 920 within the lumen 916. Inanother configuration, a limit stop, not shown, can be provided withinthe lumen 916 which prevents further insertion of the plug 920, andalerts the physician that proper placement of the plug has occurred.

Advantageously, the hydrogel seal and the expandable matrix allow foreffective sealing of the medical device or the electrode lead uponcontact with body fluid. The hydrogel seal does not significantly add tothe friction when a physician or assistant rotates the stylet to rotatethe piston, since the expanded hydrogel is lubricious, allowing movementof the internal components. The seal blocks or limits body fluids whichattempt to enter the lumen of the electrode lead.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. For instance, the seal can be used with a variety ofmedical devices. Although the use of the lead has been described for usein a cardiac pacing system, the lead could as well be applied to othertypes of body stimulating systems. In addition, the lead could also beapplicable to bipolar pacing leads having two separate conductors, andto multipolar pacing leads employing multiple conductor leads. The scopeof the invention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

1. A permanently implantable intravenous lead capable of pacing theheart, comprising: a permanently implantable elongated, flexible bodymember made of an electrically insulative material, said body memberhaving a proximal end portion and a distal end portion; a lumenextending through the body member from the proximal end portion to thedistal end portion of the body member; a conductive member extendingthrough the body member from the proximal end portion toward the distalend portion; and a sealing assembly located at a distal end portion ofthe lead, the sealing assembly including a seal coupling element havinga proximal portion, a distal portion, and a passage coaxial with thelumen and extending through the seal coupling element, the passage andlumen configured to allow for implantation of the lead over a guidewire,and the distal portion of the seal coupling element having a maximumouter diameter greater than a maximum outer diameter of the proximalportion, and a sealing element coupled to the distal portion of the sealcoupling element.
 2. The lead as claimed in claim 1, wherein the sealingelement is located within the distal portion of the seal couplingelement.
 3. The lead as claimed in claim 1, wherein the sealing elementincludes a ring shape.
 4. The lead as claimed in claim 3, wherein thesealing element has a constant inner diameter.
 5. The lead as claimed inclaim 4, wherein the sealing element has a constant outer diameter. 6.The lead as claimed in claim 1, wherein the sealing element is locatedcompletely within the distal portion of the seal coupling element. 7.The lead as claimed in claim 1, wherein the proximal portion of the sealcoupling element is located at least partially within a helical coilportion of the conductive member.
 8. The lead as claimed in claim 1,wherein the conductive member includes a helical coil portion.
 9. Thelead as claimed in claim 1, wherein a radially outer surface of the sealcoupling element includes a shoulder, and the conductive member abutsthe shoulder.
 10. The lead as claimed in claim 9, wherein the conductivemember is rigidly secured to the shoulder of the seal coupling element.11. The lead as claimed in claim 1, wherein the sealing element isconfigured to block bodily fluid from entering the lumen.
 12. The leadas claimed in claim 1, wherein the sealing element includes ananti-inflammatory additive.
 13. The lead as claimed in claim 1, whereinthe distal portion of the seal coupling element includes a uniform outerdiameter.
 14. The lead as claimed in claim 1, wherein the sealingelement is located within the seal coupling element.
 15. The lead asclaimed in claim 1, wherein the seal coupling element includes a metalalloy.
 16. The lead as claimed in claim 1, wherein the seal couplingelement is electrically coupled to the conductive member.
 17. A cardiacrhythm management device comprising a pulse generator and the lead asclaimed in claim 1 coupled to the pulse generator.
 18. A permanentlyimplantable intravenous lead capable of pacing the heart, comprising: apermanently implantable elongated, flexible body member made of anelectrically insulative material, said body member having a proximal endportion and a distal end portion; a lumen extending through the bodymember from the proximal end portion to the distal end portion of thebody member; a conductive member extending through the body member fromthe proximal end portion toward the distal end portion; and a sealingassembly located at a distal end portion of the lead, the sealingassembly including a seal coupling element having a passage coaxial withthe lumen and extending through the seal coupling element, the passageand lumen configured to allow for implantation of the lead over aguidewire and having a proximal portion received within the body member,and a sealing element coupled to the seal coupling element.
 19. The leadas claimed in claim 18, wherein the sealing element is coupled to adistal portion of the seal coupling element.
 20. The lead as claimed inclaim 18, wherein the sealing element includes a ring shape.
 21. Thelead as claimed in claim 20, wherein the sealing element has a constantinner diameter.
 22. The lead as claimed in claim 18, wherein the sealingelement is located within the distal portion of the seal couplingelement.
 23. The lead as claimed in claim 18, wherein the conductivemember includes a helical coil portion.
 24. The lead as claimed in claim18, wherein a radially outer surface of the seal coupling elementincludes a shoulder, and a distal end of the conductive member abuts theshoulder.
 25. The lead as claimed in claim 18, wherein the conductivemember is rigidly secured to the seal coupling element.
 26. The lead asclaimed in claim 18, wherein the sealing element is configured to blockbodily fluid from entering the lumen.
 27. The lead as claimed in claim18, wherein the sealing element includes an anti-inflammatory additive.28. The lead as claimed in claim 18, wherein a distal portion of theseal coupling element includes a uniform outer diameter.
 29. The lead asclaimed in claim 18, wherein the sealing element is coupled to an innerportion of the seal coupling element.
 30. The lead as claimed in claim18, wherein the seal coupling element includes a metal alloy.
 31. Thelead as claimed in claim 30, wherein the seal coupling element iselectrically coupled to the conductive member.
 32. A cardiac rhythmmanagement device comprising a pulse generator and the lead as claimedin claim 18 coupled to the pulse generator.
 33. A permanentlyimplantable intravenous lead capable of pacing the heart, comprising: apermanently implantable elongated, flexible body member made of anelectrically insulative material, said body member having a proximal endportion and a distal end portion; a lumen extending through the bodymember from the proximal end portion to the distal end portion of thebody member; a conductive member extending through the body member fromthe proximal end portion toward the distal end portion, said conductivemember comprising a helical coil portion; and a sealing assembly coupledto a distal end portion of the lead, the sealing assembly including aproximal portion located within an inner diameter of the helical coilportion, a distal portion, a passage coaxial with the lumen andextending through the sealing assembly, the passage and lumen configuredto allow for implantation of the lead over a guidewire, and a sealingelement located at the distal portion of the sealing assembly andconfigured to limit bodily fluid from entering the lumen.
 34. The leadas claimed in claim 33, wherein the sealing element includes ananti-inflammatory additive.
 35. The lead as claimed in claim 33, whereinthe sealing element is configured to block bodily fluid from enteringthe lumen.
 36. The lead as claimed in claim 33, wherein the sealingelement includes a ring shape.
 37. The lead as claimed in claim 36,wherein the sealing element has a constant inner diameter.
 38. The leadas claimed in claim 37, wherein the sealing element has a constant outerdiameter.
 39. A cardiac rhythm management device comprising a pulsegenerator and the lead as claimed in claim 33 coupled to the pulsegenerator.